JP2002312986A - Optical recording medium, processor and processing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a processor and a processing method for a terabit class rewritable (recordable) optical recording medium by which sufficiently strong regenerative signal light can be detected from a nanopit and information recording, reproduction and erasure can also be repeatedly performed. SOLUTION: This processing (recording, reproduction and erasure) device for an optical recording medium has a conductive probe (1) which faces the surface of a recording medium in contact with the surface of an optical recording medium (11) or in small space of a range in which a tunnel current is caused to flow and is acuminated so as to limit an injection area of current into a phase change recording medium within the area of a nanometer size, and is provided with a pulse power supply (9) which can apply a bias voltage pulsatively, that can cause a probe current (2) capable of heating up to a temperature at which the crystal condition of the phase change recording medium (4) is changed from a high resistance crystal to a low resistance crystal, and a probe current capable of heating up to a temperature at which the crystal condition of the phase change recording medium is changed from a low resistance crystal into a high resistance crystal to flow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION Due to the recent explosive increase in the amount of information distributed by a high-speed and wide-area communication network such as the Internet, and the dramatic increase in the size of computer software and the amount of data processed, optical information for recording such information has been increased. There is a strong demand for large capacity recording devices. In addition, various electronic devices have been miniaturized, and there has been an increasing need for small and lightweight large-capacity storage devices that can be mounted on satellites, mobile (wearable) communication devices, and the like. These were the background, the required storage capacity is several orders of magnitude increase in the short term, 1 m ² per 1550 terabits [per square inch 1 tera (1
0 ^{12: T)} bit] or more (are coveted ultra-high density of realization of terabit-class), the use range and the market size is very large (Reference: Light Industry and Technology Development Association, ed., "Light industry roadmap )). The present invention relates to an optical recording medium for realizing a rewritable (rewritable) optical recording device having an ultra-high recording surface density of the terabit class, a processing device thereof, and a processing method.

[0002]

2. Description of the Related Art Hitherto, as a rewritable recording apparatus, a magnetic recording system in which a difference in magnetization direction of a magnetic recording material is used as a recording unit has been mainly used. These include a hard disk in which a recording medium and a signal detection mechanism are integrated, and a floppy disk in which the recording medium can be carried separately from the signal detection mechanism. In recent years, there has been a remarkable development of an optical recording system in which laser light is condensed and irradiated onto a recording material by a lens, and the difference in optical characteristics of the recording material generated at that time is recorded / reproduced as a recording unit. Examples of the rewritable recording device of the optical recording system include a compact disk (CD), a digital video disk (DVD), and a magneto-optical disk (MO disk), which are widely used.

[0003]

By the way, in the recording area density of the terabit class, the size of the recording unit (pit) is 25.
It has to be extremely small, on the order of nanometers (nanometers = 10 ⁻⁹ m) or less (hereinafter, such pits of nanometer size are referred to as nanopits). Conventional magnetic recording methods include longitudinal magnetic recording and perpendicular magnetic recording, but with the currently practiced longitudinal magnetic recording, physical domain reversals cannot be maintained when the pit size reaches the nanometer level. There is a theoretical limit (supermagnetic limit). As a result, the recording surface density of the magnetic recording system is limited to about 100 gigabits (10 ⁹ : G) bits, and it is difficult to practically use a terabit-class recording device using the magnetic recording system. It has been made more perpendicular magnetization scheme high surface recording density is expected for many years research, not standing still practical prospect.

On the other hand, in the optical recording system, the current DVD and C
In optical discs such as D, the light irradiation range cannot be reduced to less than half the wavelength of light (submicron level) due to the diffraction limit of the laser beam focused by the lens, so the areal recording density is limited to about 10 Gbits, which also requires nanopits. It cannot be applied to a terabit-class recording device that performs Therefore, as a method for efficiently recording and reproducing nanopits, a method is known in which a current is injected into the nanometer region of a medium from the tip of a conductive probe, light is excited in the medium by the current, and this light is detected (current excitation light emission). Method) was proposed. As a medium for a rewritable recording device using this method, a layer (light emitting layer) which emits light by current injection on a substrate, and a material on which electric resistance and light transmittance reversibly change phase by current are further formed. What laminated | stacked the formed layer (recording layer) is used. In this method, the probe current can be intensively injected into the nanometer-sized area in the medium with little loss, so that nanopits can be formed with high efficiency.
Since there is no pumping light, there is an advantage that the SN ratio of signal light detection can be increased. However, in this conventional recording method, the phase change between the crystal and the amorphous was used for the formation of the pits. There has been a problem that a structure or the like is required to prevent the influence of heat on the substrate or the like when the temperature is raised to a very high temperature.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, and to detect a reproduction signal light of sufficient intensity from nano-pits and to perform terabit recording / reproducing / erasing of information repeatedly. An object of the present invention is to provide a rewritable (rewritable) optical recording medium of a class and a processing device and a processing method for recording, reproducing, and erasing the optical recording medium.

[0006]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, as described in claim 1, the upper part of the light emitting medium which generates light by the energy injected from the outside has a light transmitting property, and the electric conductivity changes reversibly by the energy injected from the outside. An optical recording medium configured by laminating a phase change recording medium,
The above-mentioned phase change recording medium is an optical recording medium made of a phase change recording material having at least two kinds of crystalline states having different electric resistances depending on a difference in the highest temperature reached.

[0007] Also, as described in claim 2, claim 1
Wherein the light emitting medium is a direct transition semiconductor which emits light by current injection or an optical recording medium having a well structure containing these materials.

[0008] Also, as described in claim 3, claim 1
Alternatively, in the second aspect, the phase change recording material is an optical recording medium made of a compound containing germanium, antimony, and tellurium.

According to a fourth aspect of the present invention, there is provided an optical recording medium which contacts the surface of the optical recording medium or faces the surface of the optical recording medium at a small interval within a range in which a tunnel current flows. A sharpened conductive probe is provided so that an injection region into the phase change recording medium is limited to a region of nanometer size, and the phase change recording medium is provided between the conductive probe and the optical recording medium. A probe current that can be heated to a temperature at which the crystal state of the phase change recording medium changes from a high resistance crystal to a low resistance crystal, and a probe current that can be heated to a temperature at which the crystal state of the phase change recording medium changes from a low resistance crystal to a high resistance crystal. The present invention is an optical recording medium processing apparatus provided with a pulse power supply capable of applying a bias voltage that can be applied in a pulsed manner.

[0010] Also, as described in claim 5, claim 4
In the above, the means for exciting the light emitting medium in the optical recording medium to generate light emission, and the means for condensing the light emitted from the light emitting medium have a structure in which an end face of an optical fiber or an optical waveguide is coated with a transparent electrode thin film. It is a processing device for an optical recording medium having the same.

According to a sixth aspect of the present invention, the optical recording medium is in contact with the surface of the optical recording medium or opposed to the surface of the optical recording medium at a small interval within a range in which a tunnel current flows.
Using a processing apparatus for an optical recording medium having a sharpened conductive probe so that a region where current is injected into the phase change recording medium is limited to a nanometer-sized region, the crystal state of the phase change recording medium is changed. Probe current corresponding to the recording signal is injected in pulses from the surface of the optical recording medium, which is a high-resistance crystal with high electrical resistance, and heated to a temperature at which the high-resistance crystal changes to a low-resistance crystal. And a method for processing an optical recording medium for forming recording pits composed of nano-pits of a low-resistance crystal corresponding to.

According to a seventh aspect of the present invention, the optical recording medium contacts the surface of the optical recording medium or faces the surface of the optical recording medium at a small interval within a range in which a tunnel current flows.
Using a processing device for an optical recording medium having a sharpened conductive probe so that a region where current is injected into the phase change recording medium is limited to a nanometer-sized region, a recording signal is applied to the phase change recording medium. From the surface of the optical recording medium on which the recording pits composed of the corresponding low-resistance crystal nano-pits are formed, the power within the range where the low-resistance crystal of the phase-change recording medium does not change from the probe to the recording area of the phase-change recording medium. And a method for processing an optical recording medium in which recording is reproduced by detecting light emission from a light emitting medium provided below the recording area.

According to another aspect of the present invention, the optical recording medium is in contact with the surface of the optical recording medium or opposed to the surface of the optical recording medium at a small interval within a range in which a tunnel current flows.
Using a processing apparatus for an optical recording medium having a sharpened conductive probe so that a region where current is injected into the phase change recording medium is limited to a nanometer-sized region, the crystal state of the phase change recording medium is changed. By injecting a probe current that can be heated to a temperature that changes from a low-resistance crystal to a high-resistance crystal, a method for processing an optical recording medium for erasing recording is performed.

The present invention provides a means for supplying a current to a minute area of an optical recording medium, and a phase change recording in which the electric conductivity is reversibly changed by the injection of a current in a light emitting medium which generates light by the injection of the current. An optical recording medium comprising a stacked medium and an optical recording device having means for detecting light emission from the light emitting medium, wherein the phase change recording medium has at least two different electric resistances depending on two ultimate temperatures lower than a melting temperature. Using a material that causes a phase change between different types of crystals,
By making the types of crystal states correspond to the presence or absence of pits, it is possible to realize a terabit-class rewritable optical recording device that does not cause a change in volume or a problem of heat resistance without using a high temperature required for amorphization. . The present invention can realize terabit-class rewritable optical recording / reproducing / erasing that enables optical recording / reproducing / erasing of information data with less current injection by employing the above-described materials and configurations. There is an effect that can be done.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Used for an optical recording medium of the present invention
As a phase change recording material, for example, Ge₂Sb ₂Te
₅(Hereinafter simply referred to as GeSbTe) temperature history and
FIG. 1 schematically shows the relationship between the electric resistances. First on the board
GeSbTe film immediately after sputtering is amorphous
Before use, once T1 (about 150 ℃)
Temperature range between T2 and T2 (about 350 ° C)
After heating the mixture to room temperature, the mixture returns to room temperature, and becomes the state of crystal A.
(This step is omitted in FIG. 1). Crystal A is dozens of k
Has a high electrical resistance of Ω or higher. Next, A crystal from T2
Tm (melting temperature: about 600 ° C)
Re-heated to region B)
You. Crystal B has a low electric resistance of several tens Ω. Crystal B
When it is heated to the temperature range A and cooled, it becomes the crystal A again.
As described above, GeSbTe is crystallized according to the temperature history experienced.
A changes phase between A and crystal B, and accordingly, the electric resistance becomes 3
It changes by more than an order of magnitude. Unless the temperature is higher than Tm
Never return to Rufus. That is, a GeSbTe film
Has a high-resistance crystal A and a low-resistance crystal B,
Phase change between crystal A and crystal B depending on temperature history
It shows that.

A basic embodiment of the present invention utilizing the characteristics shown in FIG. 1 will be described with reference to FIG. Where 1
Is a conductive light collecting probe, 2 is a probe current (electrons), 3 is a surface protective layer, 4 is a phase change recording medium (GeSbTe), 4
a is a region of crystal A in the phase change recording medium (initial state);
b is a region of crystal B in the phase change recording medium (referred to as nano pits), 5 is a light emitting medium, 6 is an electrode (when the substrate is insulative), 6 'is an electrode (when the substrate is conductive), 7 is substrate,
Reference numeral 8 denotes light, 9 denotes holes, 10 denotes a pulse power supply, and 11 denotes an optical recording medium.

The conductive light collecting probe 1 has a structure in which a transparent conductive film is coated on the surface of an optical fiber whose tip is sharpened to, for example, a pit size. The probe tip has both conductivity and transparency, and injects a tunnel current into the phase change recording medium 4 and collects light from the light emitting medium 5 at the same time. In this embodiment, the case where the current injection and the light collection are performed by the same probe is described. However, the current injection is performed by the conductive probe, and the light collection is performed by a light collection element (for example, a lens or a reflecting mirror) provided separately from the probe. ) Is also possible. The electrode 6 (only in the case of an insulating substrate) and the light emitting medium 5 are laminated on the substrate 7. The light-emitting medium 5 is a material or a structure that emits light when current is injected, for example, AlGa that is a direct transition semiconductor.
The phase-change recording medium 4 is laminated on a light-emitting medium 5 composed of As, GaN, InP, or the like, or a well structure containing these materials. Here, GeS is used as the phase change recording material.
An example in the case of using bTe is shown. GeSbTe immediately after being formed by sputtering is in an amorphous state.
Once this is heated together with the substrate to a temperature region A and returned to room temperature, it becomes a crystal A. It has a high electric resistance of several tens kΩ or more. This is an initial state.

FIG. 2 is a schematic diagram showing an example of the configuration of a terabit-class ultrahigh-density optical recording device according to the present invention. Although the embodiment in which a transparent and conductive probe is used as the light collecting means to collect light from the probe has been described here, a structure in which a focusing lens or a concave mirror is provided separately from the current injection probe is used. It is also applicable.

(1) Recording A probe is scanned over the medium surface of the crystal A film. When the probe comes to the position where the pit is to be formed, a probe current such that the GeSbTe film is heated to the temperature region B is injected between the probe and the medium surface in a pulsed manner. Once the GeSbTe which has experienced this temperature becomes crystal B, it returns to room temperature. The electric resistance of GeSbTe which has become crystal B is significantly reduced to several tens Ω. On the other hand, the light transmittance is almost the same as that of the crystal A. The region of the crystal B is defined as a pit. Size can be controlled by probe current and diameter is 10n
m. By repeating this operation while moving the probe, nano-pits corresponding to the recording signal are sequentially formed on the GeSbTe film. Since the temperature region B is lower than the melting temperature of GeSbTe (about 600 ° C.), recording can be performed with a smaller probe current than in the optical recording method using amorphous. Further, there is an advantage that the medium structure for heat resistance can be reduced.

(2) Reproduction Next, a probe current that does not allow GeSbTe to reach the temperature range A is injected into the medium. On the crystal A where no pits are formed, the probe current is small due to the high electric resistance,
No luminescence is detected. On the other hand, on the crystal B on which the pits are formed, a large probe current is applied to GeS due to low electric resistance.
It flows through the bTe layer. This current flows into the luminescent medium below the GeSbTe layer, and light is strongly emitted. This light is collected and detected. The emission intensity is proportional to the probe current. Since the resistance ratio between the crystal A and the crystal B is as large as at least three digits or more, the light emission intensity changes greatly depending on the presence or absence of pits. The recording can be reproduced by reading the change in the light emission intensity. It is possible to collect light with a lens or concave mirror installed separately from the probe, but it is better to use a transparent and conductive probe and use a means to collect light at the tip of the probe, Light can be detected with higher sensitivity. When the light emitting medium has the electron confinement structure, the injected current is localized in a narrow space of the light emitting medium immediately below the probe, so that the efficiency of light collection by the probe can be increased.

(3) Erasing After heating the crystal B again to the temperature range A and then cooling it to room temperature, the phase changes to the crystal A and the crystal B disappears. Thereby, the nanopits, that is, the recorded data can be erased. At room temperature, both the crystal A and the crystal B are stable, so that the nanopit recording, reading (reproducing), and erasing operations required for the terabit optical recording device can be realized.

[0022]

According to the optical recording medium, the processing apparatus and the processing method of the present invention, a terabit-class ultra-high-density terabit-class stably operated with a smaller probe current than an optical recording apparatus utilizing an amorphous state. A rewritable optical recording device can be realized.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a temperature history and electric resistance of Ge ₂ Sb ₂ Te ₅ which is a phase change recording material exemplified in the embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a terabit-class ultra-high-density optical recording device exemplified in the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Conduction condensing probe 2 ... Probe current (electron) 3 ... Surface protection layer 4 ... Phase change recording medium 4a ... Crystal A area (initial state) 4b ... Crystal B area (nanopit) 5 ... Light emitting medium 6 ... Electrode (When the substrate is insulative) 6 '... Electrode (When the substrate is conductive) 7 ... Substrate 8 ... Light 9 ... Hole 10 ... Pulse power supply 11 ... Optical recording medium

Claims (8)

[Claims] 1. A phase-change recording medium having a light-transmitting property and having an electric conductivity reversibly changed by externally injected energy is provided above a light-emitting medium which generates light by externally injected energy. An optical recording medium formed by lamination, wherein the phase-change recording medium has at least two electric resistances that differ according to a difference in maximum temperature reached.
An optical recording medium comprising a phase change recording material having various crystal states. 2. An optical recording medium according to claim 1, wherein said light emitting medium has a direct transition type semiconductor emitting light by current injection or a well structure containing these materials. 3. An optical recording medium according to claim 1, wherein said phase change recording material comprises a compound containing germanium, antimony and tellurium. 4. A region for injecting current into the phase-change recording medium, wherein the region is in contact with the surface of the optical recording medium or at a minute interval within a range in which a tunnel current flows, facing the surface of the optical recording medium. It has a sharpened conductive probe so as to be limited to the nanometer-sized region, and between the conductive probe and the optical recording medium, changes the crystal state of the phase-change recording medium from a high-resistance crystal to a low-resistance crystal. A bias voltage that allows a probe current that can be heated to a temperature at which the crystal state of the phase change recording medium is changed from a low-resistance crystal to a high-resistance crystal to a probe current that can be heated to a temperature at which the phase change recording medium changes to a high-resistance crystal to be pulse-like is applied. An optical recording medium processing apparatus, comprising: a pulse power supply that can be applied to an optical recording medium. 5. The optical recording medium according to claim 4, wherein the means for exciting the light emitting medium in the optical recording medium to generate light emission and the means for condensing light emitted from the light emitting medium are provided on an end face of an optical fiber or an optical waveguide. An optical recording medium processing apparatus having a structure coated with a transparent electrode thin film. 6. A region in which a current is injected into the phase change recording medium in contact with the surface of the optical recording medium or at a small interval in a range in which a tunnel current flows, and the current is injected into the phase change recording medium in a nanometer range. An optical recording medium in which the crystal state of the phase-change recording medium is a high-resistance crystal having a high electric resistance, using an optical recording medium processing apparatus having a sharpened conductive probe so as to be limited to the area of the size. A probe current corresponding to a recording signal is injected in a pulsed manner from the surface of the substrate, and heated to a temperature at which a high-resistance crystal changes to a low-resistance crystal to form a recording pit comprising nano-pits of a low-resistance crystal corresponding to the recording signal. A method for processing an optical recording medium, comprising: 7. A region in which a current is injected into the phase-change recording medium in contact with the surface of the optical recording medium or at a minute interval in a range in which a tunnel current flows. Using a processing device for an optical recording medium having a sharpened conductive probe so as to be limited to the area of the size, a recording pit composed of nano-pits of a low-resistance crystal corresponding to a recording signal is formed on the phase-change recording medium. From the surface portion of the optical recording medium, a power within a range where the low-resistance crystal of the phase change recording medium does not change is injected from the probe into the recording region of the phase change recording medium, and provided below the recording region. A method for processing an optical recording medium, wherein recording and reproduction are performed by detecting light emission from an existing light emitting medium. 8. A phase in which current is injected into the phase-change recording medium in contact with the surface of the optical recording medium or at a minute interval within a range in which a tunnel current flows. Using a processing apparatus for an optical recording medium having a sharpened conductive probe so as to be limited to the area of the size, heating to a temperature at which the crystal state of the phase change recording medium changes from a low-resistance crystal to a high-resistance crystal. A method for processing an optical recording medium, wherein the recording is erased by injecting a probe current that can be used.